1. Field of the Invention
The present invention relates to a process for regeneration of a thick layer transferred wafer obtained by forming a laminated body by laminating a semiconductor wafer onto which implanted into a support wafer and by separating from a thin layer of the semiconductor wafer in the ion implanted area by heat treatment of this laminated body and a layer transferred wafer regenerated by this process. The present invention relates more particularly to a process for regeneration of a layer transferred wafer regenerated in the so-called ion implantation separation method for producing bonded wafers such as SOI (Silicon On Insulator) and a regenerated wafer.
2. Description of the Related Art
As a conventional process for manufacturing an SOI wafer, a process is known in which an ion is implanted on a main surface of a semiconductor wafer to form an ion implanted area inside the semiconductor wafer, a main surface of the semiconductor wafer is laminated on a main surface of a support wafer to form a laminated body, the laminated body is subjected to heat treatment at a predetermined temperature and the ion-implanted wafer is separated after bonding so as to manufacture the SOI wafer. The semiconductor wafer and the support wafer used in this method have the same diameter and the same thickness are used, and this is a technology to obtain an SOI wafer in which the semiconductor wafer is separated to be a thin film with the ion implanted area implanted on the main surface of the semiconductor wafer as a cleaved surface and the support wafer is thermally treated with the thin film to reinforce bonding. With this method, the cleaved surface is a favorable mirror surface, and an SOI wafer whose the film thickness has high uniformity is obtained relatively easily.
On the other hand, when a bond wafer such as the SOI wafer is made with this ion-implanting layer transferring method, a single layer transferred wafer is inevitably sub-generated. In this ion-implanting layer transferring method, by regenerating this sub-generated layer transferred wafer, a plurality of SOI wafers can be obtained using a substantially single semiconductor wafer, which can considerably reduce the cost.
However, a wafer is usually chamfered, and even if the wafers with the same outer diameter are laminated together, all the peripheries are not in contact. And when the semiconductor wafer is separated to be a thin film with the ion implanted area as the cleaved surface, its periphery remains not separated, and there is a problem that a step is generated in the periphery of the regenerated layer transferred wafer. Also, a damage layer due to ion-implanting exists on the separated surface of the layer transferred wafer and the surface roughness can be large, which makes it difficult to use the layer transferred wafer as it is. Therefore, it is necessary to remove the steps and damage layer and to reduce surface roughness for regeneration of this layer transferred wafer, and it is also necessary to prevent generation of particles caused by an ion implanted layer remaining on the step.
As a conventional process for regeneration of a layer transferred wafer, a process for regeneration of a layer transferred wafer is known in which after an ion implanted layer remaining on the step in the periphery of the separated surface of the layer transferred wafer is removed by chamfering or etching, a main surface of the wafer on the layer-transferred side is polished (See the patent document 1, for example). According to this process for regeneration, since the removal of the ion implanted layer is performed by chamfering or the like, after that, the so-called mirror polishing (mirror chamfering) is performed on the face which has become rough due to the chamfering or the like. By this process for regeneration of a layer transferred wafer, the generation of particles caused by existence of the ion implanted layer is prevented by removing the ion implanted layer, the damage layer on the surface of the layer transferred wafer is removed, and the surface roughness of the layer transferred wafer can be improved.
[Patent Document 1] Japanese unexamined Patent Application No. 2001-155978 (claim 1, Paragraphs 0032 and 0052).
However, by the conventional process for regeneration of a layer transferred wafer shown in the patent document 1, since the ion implanted layer is removed by chamfering or etching and then subjected to mirror polishing, the surface roughness of the layer transferred wafer can be reduced, but the problem is that more time is required to regenerate the layer transferred wafer and the number of times capable of regeneration is decreased since a removal amount of a wafer to be processed is relatively increased due to grinding.
An object of the present invention is to provide a process for regeneration of a layer transferred wafer which can reduce the regeneration cost by reducing a processing time required for the regeneration of the layer transferred wafer and increase the number of regeneration times by decreasing a removal amount at the regeneration and a regenerated wafer.